The present invention is directed to a method for manufacturing preforms coated with hard solder for repairing interconnect interruptions, particularly for repairing meander-shaped interconnects whose width, for example, lies in the range from 50 through 70 .mu.m.
For repairing regularly occurring interconnect interruptions, preforms corresponding to the interconnect structure are placed bridge-like on the defective interconnect approximately congruently relative to the interconnect in the area of the interrupt or defect and are joined to the interconnect at both sides of the interruption. German Patent 2 251 997 discloses a method with which such preforms that are composed of a fine band coated with hard solder are processed. German Publish Application 30 25 875 discloses an apparatus related thereto for repairing interconnect interruptions. This prior art apparatus is composed of an electrode system that produces the connection between a preform and an interconnect by resistance heating. Interconnects and corresponding preforms having a width of about 100 through 150 .mu.m are disclosed in both publications. As a consequence of their relatively large dimension, such preforms can be punched with a press tool. A completely plated preform results following the punching process due to the use of a plated metal band.
Since technical progress has now made possible a miniaturization of the interconnects down to a width of 50 through 70 .mu.m, for example, a correspondingly small preform is required for repairing these interconnects. However, traditional pressing techniques, when a preform is punched with a punch that has the same geometry, fail here. Utilizing the etching techniques standard for the manufacture of printed circuits for producing the abovedescribed preforms has similar difficulties. A metal band that has already been plated is etched to different degrees by an etchant, i.e. is etched very differently dependent on the existing material. This leads to pronounced under-etchings of the preform, when, for example, a preform plated with hard solder is manufactured from a copper band plated with hard solder. The etchant attacks the copper band, the substrate, far more extensively than it attacks the hard solder plating. The use of different etchants has not lead to a satisfactory result in the prior art.